1. Field of the Invention
The present invention relates to a novel polyhydroxyalkanoate (PHA) and its production method. Further, the present invention relates to a charge control agent, a toner binder, an electrostatic latent image developing toner, and an image forming method and an image forming apparatus using the toner which are employed for a recording method utilizing electrophotograph, electrostatic recording, magnetic recording and the like. Particularly, the present invention relates to a charge control agent, a toner binder, an electrostatic latent image developing toner, an image forming method and an image forming apparatus which are employed for electrophotography, electrostatic recording, electrostatic printing of such as a copying apparatus, a printer, a facsimile and the like for forming an image by previously forming a toner image on an electrostatic latent image carrier (hereinafter, referred to simply as “image carrier”) and then transferring the image to a transfer material. More particularly, the present invention relates to a negatively charged charge control agent, a toner binder using the agent, an electrostatic latent image developing toner, and an image forming method and an image forming apparatus using the toner.
2. Related Background Art
So far, many types of microorganism have been reported to produce poly-3-hydroxybutyric acid (PHB) or other PHA and internally accumulate it (Biodegradable Plastic Handbook, Biodegradable Plastic Research Associate, N.T.S. Co., Ltd., p. 178-197 (1995)). Similarly to conventional plastics, these polymers are usable for production of a variety of products by melting and processing. Further, owing to the biodegradability, they have an advantage that they can be completely decomposed by microorganism in the nature and do not have a problem many synthetic polymer compounds of remaining in the natural environments and causing pollution. Also, they are excellent in bio-compatibility and highly expected to be applied to soft members or the like for medical use.
It is known that such microorganism-producing PHA may have various compositions and structures depending on the type of the microorganism to be employed for the production, the culture medium composition, and the culture conditions, and researches regarding mainly control of such compositions and structures have been performed in terms of improvements of the physical properties of PHA.
[1] At first, the biosynthesis of PHA, which is a polymer obtained by polymerizing a monomer unit with a relatively simple structure such as 3-hydroxybutyric acid (hereinafter abbreviated as 3HB) and the like, can be exemplified as follows:
(a) those containing 3HB and 3-hydroxyvaleric acid (hereinafter abbreviated as 3HV); Japanese Patent Publication No. 6-15604, Japanese Patent Publication No. 7-14352, Japanese Patent Publication No. 8-19227, Japanese Patent Application Laid-Open No. 5-7492;
(b) those containing 3HB and 3-hydroxyhexanoic acid (hereinafter abbreviated as 3HHx); Japanese Patent Application Laid-Open No. 5-93049, Japanese Patent Application Laid-Open No. 7-265065;
(c) those containing 3HB and 4-hydroxybutyric acid (hereinafter abbreviated as 4HB); Japanese Patent Application Laid-Open No. 9-191893;
(d) those containing 3-hydroxyalkanoate of 6 to 12 carbons; Japanese Patent Publication No. 2,642,937; and
(e) those produced by biosynthesis from a single aliphatic acid as a carbon source (the products are approximately the same as those of (d), Appl. Environ. Microbiol., 58 (2), 746 (1992)). They are all PHA composed of monomer units having alkyl groups in the side chains and synthesized by β-oxidation of hydrocarbons or fatty acid synthesis from saccharides by microorganism, in other words, “usual PHA”.
[2] However, taking into account of a wide range application of such microorganism producing PHA (“unusual PHA”), for example, application as functional polymers, PHA into which substituent groups other than alkyl groups are introduced for the side chain is supposed to be extremely advantageous. Examples of the substituent groups are those containing aromatic ring (phenyl, phenoxy, benzoyl and the like), unsaturated hydrocarbons, ester groups, allyl, cyano, halogenated hydrocarbons, epoxide and the like. Among them, PHA having an aromatic ring has actively been investigated.
(a) Those containing phenyl or its partially substituted groups
Makromol. Chem., 191, 1957-1965 (1990) and Macromolecules, 24, 5256-5260 (1991) report production of PHA containing 3-hydroxy-5-phenylvaleric acid as a unit from 5-phenylvaleric acid as a substrate by Pseudomonas oleovorans. 
Macromolecules, 29, 1762-1766 (1996) reports production of PHA containing 3-hydroxy-5-(4′-tolyl)valeric acid as a unit from 5-(4′-tolyl)valeric acid as a substrate by Pseudomonas oleovorans. 
Macromolecules, 32, 2889-2895 (1999) reports production of PHA containing 3-hydroxy-5-(2′,4′-dinitrophenyl)valeric acid and 3-hydroxy-5-(4′-nitrophenyl)valeric acid as a unit from 5-(2′,4′-dinitrophenyl)valeric acid as a substrate by Pseudomonas oleovorans. 
(b) Those containing phenoxy group or its partially substituted groups
Macromol. Chem. Phys., 195, 1665-1672 (1994) reports production of PHA copolymer of 3-hydroxy-5-phenoxyvaleric acid and 3-hydroxy-9-phenoxynonanoic acid from 11-pheoxyundecanoic acid as a substrate by Pseudomonas oleovorans. 
Japanese Patent Publication No. 2,989,175 discloses the invention relating to homopolymers of 3-hydroxy-5-(monofluorophenoxy)pentanoate (3H5(MFP)P) unit or 3-hydroxy-5-(difluorophenoxyl)pentanoate (3H5(DFP)P) unit; copolymers containing at least (3H5(MFP)P) unit or (3H5(DFP)P) unit; Pseudomonas putida for synthesizing these polymers; and a production method of the polymers using the Pseudomonas species and describes the effects that a polymer having phenoxy group substituted with 1 or 2 fluorine atoms in the side chain terminal can be synthesized by metabolizing a long chain aliphatic acid having substituent groups and that the polymer is provided with a high melting point and excellent processibility as well as stereostructure regularlity and water repelling property.
Investigations of cyano- or nitro-substituted substances other than such fluorine-substituted substances have been performed.
Can. J. Microbiol., 41, 32-43 (1995) and Polymer International, 39, 205-213 (1996) report the production of PHA containing 3-hydroxy-p-cyanophenoxyhexanoic acid or 3-hydroxy-p-nitrophenoxyhexanoic acid as a monomer unit from octanoic acid together with p-cyanophenoxyhexanoic acid or p-nitrophenoxyhexanoic acid as substrates using Pseudomonas oleovorans ATCC 29347 strain and Pseudomonas putida KT 2442 strain.
These reports are useful for obtaining polymers which all contain PHA having aromatic ring in the side chain, dissimilar to general PHA having alkyl groups in the side chain, and are provided with physical properties derived from such PHA.
(3) Also, in a new category, not within an extent to simple alteration of physical properties, productions of PHA having reactive functional groups in the side chains have been investigated to provide new functions based on the functional groups.
For example, Macromolecules, 31, 1480-1486 (1996) and Journal of Polymer Science: Part A: Polymer Chemistry, 36, 2381-2387 (1998) report that PHA containing highly reactive epoxy group in the side chain terminals can be synthesized by synthesizing PHA containing a unit having a vinyl group in the terminal of the side chain and then epoxylating the PHA by an oxidizing agent.
Also, as a synthesis example of PHA containing a unit having thioether expected to have a high reactivity, other than vinyl group, Macromolecules, 32, 8315-8318 (1999) reports production of PHA copolymer of 3-hydroxy-5-(phenylsulfanyl)valeric acid and 3-hydroxy-7-(phenylsulfanyl)valeric acid from 11-(phenylsulfanyl)valeric acid as a substrate by Pseudomonas putida 27 N 01 strain.
So far, many methods have been proposed as the electrophotography in the present invention and generally, a typical method is carried out by forming an electric latent image on an image carrier (photosensitive member) by a variety of means using a photoconductive substance, developing the latent image by a toner to obtain a visible image, transferring the toner image to a transfer material such as paper based on the necessity, and then fixing the toner image to a transfer material by heat and/or pressure to obtain a copy. As a method for visualizing the electric latent image, a cascade development method, a magnetic brush development method, a pressurizing development method and the like have been known. Further, a method using a magnetic toner and a rotary development sleeve having a magnetic pole in the center for flying the magnetic toner from the development sleeve to the photosensitive member in a magnetic field has also been employed.
The development systems to be employed for the development of an electrostatic latent image include a two-component development system using a two-component type developer containing a toner and a carrier and a monocomponent type development system using a monocomponent type developer containing only a toner without using a carrier.
A coloring fine particle generally called as a toner contains a binder resin and a coloring material as essential components and a magnetic powder as other components based on the necessity. For providing electric charge to the toner, it is possible to use the charging property of the binder resin itself without using a charge control agent, however in such a case, the stability of the electric charge with the lapse of time and the moisture resistance are inferior to make it impossible to obtain images with excellent quality. Accordingly, normally for the purpose of electric charge retention and charge control of a toner, a charge control agent is added.
Today, charge control agents known in this technical field are, for example, as negative friction charging agents, azo dye-metal complexes, aromatic dicarboxylic acid-metal complexes, salicylic acid derivative-metal complexes and the like. As positive friction charging agents, nigrosine type dyes, triphenylmethane type dyes, a variety of quaternary ammonium salts, and organic tin compounds such as dibutyl tin oxide are well known.
Recently, from a viewpoint of environment preservation, it is globally desired to further decrease wastes and prevent environmental pollution suppression. Such requirements are similarly required in electrophotography and along with the wide spread of imaging apparatuses, printing papers, used waste toner, wastes of copying papers have been increased year by year and in terms of global environment preservation, further decrease of wastes and substance consumption with consideration of environments have been required.
As means for solving the above-described problems, possibility of use of colorless compounds free from heavy metals and polymer type charge control agent has been studied. Examples of such compounds are exemplified in U.S. Pat. No. 4,480,021, U.S. Pat. No. 4,442,189, U.S. Pat. No. 4,925,765, Japanese Patent Application Laid-Open No. 60-108861, Japanese Patent Application Laid-Open No. 61-3149, Japanese Patent Application Laid-Open No. 63-38958, Japanese Patent Application Laid-Open No. 63-88564 and the like and these compounds do not have a sufficient function as the charge control agent and insufficient in the charging capability, the charge rising characteristics, the stability with the lapse of time and environmental stability. Generally, as a polymer charge control agent in the case of providing negative charging property to a toner, copolymers of styrene and/or α-methylstyrene with sulfonic acid group-containing alkyl (meth)acrylate ester or alkyl (meth)acrylamide (Japanese Patent Application Laid-Open No. 7-72658, Japanese Patent Application Laid-Open No. 8-179564, Japanese Patent No. 2,114,410, Japanese Patent No. 2,623,684, and Japanese Patent No. 2,807,795) are employed in many cases. Such materials are advantageous in a point that they are colorless, however a large amount of the materials is required to be added in order to obtain an aimed electric charge and also the sulfonic acid group is an anionic functional group and obviously has moisture absorptivity and thus the materials are supposed to have problems in terms of the moisture resistance. Further, the compatibility of these materials with a binder resin (binder) which is basically nonionic is supposed to become a problem.
From a viewpoint of the environment preservation, decomposable resin with the lapse of time by function of microorganism or the like, that is, biodegradable resin, has been developed and, for example, as described above, there is reported that a variety of microorganism produces biodegradable resin (PHA) having polyester structure and internally accumulates the resin. Such PHA is known to have various compositions and structures depending on the types of microorganism, the culture medium compositions, the culture conditions and the like and so far, researches regarding mainly control of such compositions and structures have been performed in terms of improvements of the physical properties of PHA.
In a field of electrophotography, application of biodegradable resin to binder resin especially in toner production has been proposed. For example, toners of compositions containing biodegradable resin, particularly, polyhyroxybutyric acid, polyhydroxyvaleric acid and their copolymers or blends are disclosed in U.S. Pat. No. 5,004,664. Also, Japanese Patent Application Laid-Open No. 6-289644 discloses electrophotographic toners especially for thermal roll fixation which are characterized in that at least the binder resin contains plant-derived wax and biodegradable resin (e.g., biologically produced polyesters, plant- or animal-derived natural polymer materials) and the plant-derived wax is added in an amount of 5 to 50% by weight in the binder resin. Also, Japanese Patent Application Laid-Open No. 7-120975 discloses electrophotographic toners containing lactic acid-based resin as the binder resin. Further, Japanese Patent Application Laid-Open No. 9-274335 discloses electrostatic latent image developing toners containing polyester resin obtained by dehydration condensation polymerization of compositions containing lactic acid and tri- or higher-functional oxycarboxylic acids and a coloring agent. Also, Japanese Patent Application Laid-Open No. 8-262796 discloses electrophotographic toners containing a binder resin and a coloring agent and characterized in that the binder resin is biodegradable resin (e.g., aliphatic polyester resin and the like) and the coloring agent is a non-aqueous coloring material. Also, Japanese Patent Application Laid-Open No. 9-281746 discloses electrostatic latent image developing toners containing urethane-modified polyester resin obtained by cross-linking polylactic acid with tri- or higher-functional isocyanate and a coloring agent. Any one of the above-described electrophotographic toners contains biodegradable resin and is regarded to be effective to contribute preservation of the environments.
Regarding any one of the above-described electrophotographic toners using biodegradable resin, the charge control agent contains a heavy metal such as chromium, cobalt, nickel, copper, zinc, iron and the like. On the other hand, so far, there has been no report of the case of using biodegradable resin for the charge control agent and development of a material with further consideration of the environments is thus desired.